EUV delay forces tool makers to check other options

This does not come as a surprise, but extreme ultraviolet (EUV) lithography is delayed again and is now targeted for chip production at the 16nm half-pitch node.

That's the bad news. Here's more bad news: Now, the industry faces dreaded double-patterning or some variation of the technology. Double-patterning adds cost and complexity to chip production.

There was some hope that EUV would be ready for the latter part of the 22nm half-pitch node, which is slated for the 2011 timeframe. But once again, EUV has been delayed due to lack of power sources, resists, defect-free masks and metrology tools.

"EUV looks very, very promising," said Kazuo Ushida, president of Nikon Corp.'s Precision Equipment Co., but "EUV has a long ways to go to meet the 22nm half-pitch node."

The latest concern is the EUV metrology tools, which are not available today. "It will take two years (to devise) the EUV metrology tools," Ushida said but noted that EUV will miss the window at 22nm by then.

So now what? Nikon and its rival, ASML Holding NV, are racing each other to ship next-generation, 193nm immersion tools.

Nikon is shipping a slightly new version of its 193nm immersion tool, which is geared for 32nm chip production and below. Dubbed the NSR-S620D, the tool features a lens with a numerical aperture (NA) of 1.35. The first version of the S620, which was shipped last year, had an NA of 1.30. As reported, it will also make use of a new platform, dubbed the Streamlign. Overlay is 2nm and throughput is 200 wafers an hour.

Meanwhile, ASML's TwinScan NXT:1950i system is a dual-stage, 193nm immersion lithography tool designed for volume production 300-mm wafers at the 32nm node and beyond. Building on the in-line catadioptric lens design concept of the XT:1950Hi, the NXT:1950i has a numerical aperture (NA) of 1.35.

But to extend 193nm lithography, chip makers must also evaluate and possibly use a host of so-called extension technologies.

It's a complex assortment of jargon: computational lithography, double-pattering, line cutting, source-mask optimization, among others. Here are some of the options to extend 193nm and some commentary on each technology:

Double-patterning (and its three main flavors)
Litho-Etch-Litho-Etch—This "uses one litho step followed by one etch step, which is then followed by another round of litho and etch steps," according to Barclays Capital. "Each of the litho steps is a critical litho step and therefore the overlay, i.e. how one litho step places a pattern with respect to the other is important."